Absorbent articles such as disposable diapers, adult incontinent pads, sanitary napkins and the like are generally provided with an absorbent core material to receive and retain body liquids. Typical compositions of absorbent core materials are particulate, absorbent, polymeric compositions, often referred to as “hydrogels” or “superabsorbents”, which are capable of absorbing large quantities of liquids such as water and body exudates. Fibrous components such as pulp or other synthetic fibers are incorporated into the composite together with the superabsorbent to provide acceptable fluid handling characteristics of fast liquid intake, liquid capture and reduced “gel blocking”. Gel blocking is a phenomenon that occurs when the swelling of the absorbent particles as a result of liquid absorption increases the resistance to liquid flow within the material. It is generally believed that the fibrous component provides stable interparticle liquid channels that minimize the gel blocking effect.
For fit, comfort and aesthetic reasons, it is highly desired to make disposable absorbent articles as thin as possible. Disposable absorbent articles can be reduced in thickness by reducing the absorbent core thickness. Thinner diapers are less bulky to wear, fit better and provide more comfort to the wearer. To achieve the lowest absorbent core thickness for a given level of absorbent capacity, the superabsorbent content is preferably increased toward 100%, that is, the fiber component of the absorbent core is reduced to near zero percent. The composite of superabsorbent content and fiber component oftentimes is also subjected to densification to achieve and maintain reduced thickness. However, such absorbent composites generally display much slower liquid intake characteristics due to their high composite density, high gel blocking characteristics, low permeability to liquid passage that that cause liquid leakage. In addition, higher stiffness and rigidity of such structures lead to absorbent products with poor fit and comfort.
As disclosed in prior art, the slower liquid intake of superabsorbent-containing absorbent cores can be compensated for by adding liquid-holding layers of materials on top of the absorbent core. These are usually fibrous or film structures capable of accepting the liquid insult at its rate of delivery and temporarily holding the liquid until the absorbent core can fully absorb and retain the insult. These elements are termed surge or acquisition layers, as shown in U.S. Pat. No. 5,364,382. However, increasing the number of surge layers to compensate for a much slower absorbing core adds to the thickness and cost of the absorbent article.
Other approaches such as discontinuous and patterned placement of the superabsorbent material or composite have been disclosed in the art, such as U.S. Pat. Nos. 4,560,372 and 5,868,724. Voids are created in the absorbent composite, hence the surface coverage of the absorbent composite is less than 100%. Implementation of approaches is relatively complex. Furthermore the full area available for absorbency is not utilized, and consequently the article is thicker than one with a relatively uniform distribution of superabsorbent material.
Hence, there remains a need for an absorbent core that is thin, having high absorbent capacity with good fluid intake rate characteristics, soft, and flexible that can be used in absorbent articles such as disposable diapers, adult incontinent pads or briefs, sanitary napkins and the like.